In the scanning of micro-documentation, such as aperture cards, to produce digital data from which the document can be reproduced with a sufficiently high degree of resolution, a typical aperture card may require approximately 80,000,000 discrete scan points to achieve the proper visual resolution. This number of bits would be required, for example, to scan an E-size engineering drawing reduced to a 35mm film size aperture card and store digitized reproductive data for same.
This magnitude of data bits, however, is too much data to store or handle efficiently and must be compacted, preferably before such data is translated to a data base.
Currently, such high resolution scanners scan on a line-by-line raster basis and the compaction methods for the resultant data are limited by this technique. For the typical aperture card identified above, for example, the data compaction ratio will be on the order of 50 to 100 to 1. To make such a scanner system practical the data compaction ratio should be on the order of 500 to 1000 to 1.